1. Field of the Invention
This invention relates to wireless communications and, more particularly, to a system for determining cell coverage in a wireless communications system using location information for a wireless unit.
2. Description of Related Art
FIG. 1 depicts a schematic diagram of a wireless communications system 10 which provides wireless communications service to a wireless unit 12 that is situated within a geographic region 14. A Mobile Switching Center 18 is responsible for, among other things, establishing and maintaining calls between wireless units and calls between a wireless unit and a wireline unit (e.g., wireline unit 20). As such, the MSC interconnects the wireless units within its geographic region 14 with a public switched telephone network (PSTN) 22. The geographic area serviced by the MSC is divided into spatially distinct areas called xe2x80x9ccells.xe2x80x9d As depicted in FIG. 1, each cell is schematically represented by one hexagon in a honeycomb pattern; in practice, however, each cell has an irregular shape that depends on the topography of the terrain surrounding the cell. Typically, each cell contains a base station (e.g. base stations 24a-g), which comprises the radios and antennas that the base station uses to communicate with the wireless units in that cell. The base stations also comprise the transmission equipment that the base station uses to communicate with the MSC 18 in the geographic area 14 via communication links 26a-g. One cell site may sometimes provide coverage for several sectors. In this specification, cells and sectors are referred to interchangeably.
In a wireless cellular communications system, a base station and a wireless unit communicate voice and/or data over a forward link and a reverse link, wherein the forward link carries communication signals over at least one forward channel from the base station to the wireless unit and the reverse link carries communication signals on at least one reverse channel from the wireless unit to the base station. Within the geographic region 14, the MSC 18 switches a call between base stations in real time as the wireless unit 12 moves between cells, referred to as a handoff. There are many different schemes for determining how wireless units and base stations communicate in a cellular communications system. For example, wireless communications links between the wireless units and the base stations can be defined according to different radio protocols, including time-division multiple access (TDMA), Frequency Division Multiple Access (FDMA), code division multiple access (CDMA) and others.
Currently, in FDMA, TDMA, CDMA and Global System for Mobile Communications (GSM), cell site planning is required to determine the geographic coverage for a cell. Cell site planning is a manually intensive task that needs constant adjustment. In planning a cell, the topology of the geographic area and a suitable antenna site is selected based on availability and zoning rules. Such a selection is typically not optimal but adequate. Drive tests and manually collecting signaling data are then performed mostly on the perimeter of the coverage area. Transmit and receive antennas and power are then adjusted in a manually iterative manner to improve the call quality. Sometimes, frequencies are swapped with neighbor cells and/or transmit power is readjusted to improve the coverage. Over time, the cell site engineers review customer complaints and cell site dropped call reports and again try to manually optimize the RF performance.
The present invention involves a system for determining coverage in a wireless communications systems using location information for a wireless unit and collecting information on communications between the wireless unit and the wireless communications system in association with the location information. The wireless communications system determines and/or receives location information for the wireless unit along with other information associated with the location information. The information by location can be used to represent the coverage of a geographic region. For example, during communications between a serving base station and a wireless unit, the serving base station could receive and/or determine signal quality measurements of a forward link and/or of a reverse link at a particular location. Additionally, neighboring base stations can monitor the communications and determine and/or receive location information for the location of the wireless unit along with the information associated with or corresponding to the location of the wireless unit. The associated information can be linked with additional parameters, such as wireless unit type, wireless unit identity, frequency, operating conditions and/or base station identity. In accordance with other aspects of the present invention, the information and/or measurements stored by location can be used to derive additional and/or different information by location or determine how the wireless communications system communicates with a wireless unit at a location, for example the base station to service the wireless unit at the location. A wireless unit in a location or range of location(s) could be served by a serving base station(s) at a certain transmit power and frequencies given certain operating conditions or parameters, such as time, weather, traffic load, path loss and/or interference level. A change in operating condition could trigger a dynamic change in the RF coverage provided by the serving base station(s) and/or neighboring base stations to the wireless unit(s) in the location or range of locations.